During operation of a spark ignition engine, an ignition system produces an output (e.g., breakdown voltage, peak secondary coil current, and spark duration) used to initiate combustion of a charge (e.g., mixture of air and fuel) in an engine cylinder. If the chemical and physical properties of a given charge have lower ignitability, ignition output for combustion is greater than an ignition output for another charge having higher ignitability. Engines including devices and systems, such as a compressor providing boosted air, an exhaust gas recirculation (EGR) system, and variable valve control (VVC) systems controlling, e.g., timing, duration and lift, may all impact charge ignitability, leading to increased ignition system output requirements.
In one approach, an ignition system produces a modular output. High ignition output is used under some conditions, such as during light load operating conditions when spark duration may be increased. Further, during high load and/or high dilution conditions peak secondary current and breakdown voltage may be increased.
The inventors herein have recognized issues with the above described approach. Parasitic efficiency losses are incurred when ignition output is increased, partially cancelling the efficiency benefits of high dilution and/or boosted engines. Further, increasing the range of ignition output may drastically increase ignition systems cost. Further still, without a wide range of ignition system output capabilities, an engine may not aggressively utilize lean burn, EGR, variable valve control, boost, etc. while avoiding misfires, excessive spark plug electrode erosion and the like.
Consequently, systems, devices and methods are disclosed for ignition control for an engine, such as a multi-fuel engine with a reformer for generating reformed fuel. In one example, a method for an engine includes adjusting a spark duration of a spark plug included in an ignition system, the spark plug coupled to a cylinder of the engine, the adjusting based on a reformate amount in a reformate storage tank. In a further example, a method for an engine includes adjusting a charge reformate concentration in a cylinder of the engine, the engine including an ethanol-based fuel reformate system including a reformate catalyst, the adjusting based on a spark duration of a spark plug included in an ignition system of the engine, the spark plug coupled to the cylinder.
An engine including a fuel reformer system, e.g., an ethanol based fuel reformate system, may increase charge ignitability by increasing reformate, thus alleviating the use of increased ignition system output. Consequently, lean burn, EGR, boost, VVC (or similar systems such as cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT), variable valve lift (VVL), etc.) and the like may be more aggressively utilized while reducing potential engine misfire. For example, when operating with an increased reformate amount, higher EGR levels, and/or more retarded valve timing, may be used. Additionally, there is an unexpected synergy such that increased ignition output may be used to conserve reformate.
It will be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description, which follows. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined by the claims that follow the detailed description. Further, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.